Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

A Study of Effective Deployment in Ultra-Low-Permeability Reservoirs With Non-Darcy Flow

Abstract

Due to the existence of a threshold pressure gradient (TPG) in ultra-low-permeability reservoirs, the peripheral reserves of the wellbore are difficult to deploy effectively. The main problem is that it is hard to ensure that well pattern, well spacing, and drawdown pressure easily and accurately because of the existence of low-velocity non-Darcy flow in such reservoirs. Simple and accurate calculation methods of the problem are most popular with reservoir engineers, so effective deployment calculation methods of ultra-low-permeability reservoirs are presented in this article. They include control radius calculation, control distance calculation, control area calculation, and control coefficient calculation, which can be directly used in the evaluation of well pattern thickening of developed oilfields and reserves of undeveloped oilfields. Based on theory of fluid mechanics in porous medium considering TPG, the non-Darcy flow mathematic model was established to reveal the characteristics of pressure distribution of ultra-low-permeability reservoirs. According to the analytical solution of non-Darcy radial flow, the relationship between control radius for ultra-low-permeability medium and TPG under different drawdown pressures was established. A calculation method combined with ellipse flow theory for control coefficient is presented, which was used to characterize the producing degree of reserve in a rectangular pattern. The control radius and coefficient of ultra-low-permeability reservoirs can provide a theoretical foundation for reservoir evaluation and development design.     

Differential interaction of seed polyphenols from grapes collected at different maturity stages with the protein fraction of saliva

Grape seed and skin proanthocyanidins undergo significant changes during grape maturation. Those changes have been associated with a decreased astringency of grapes collected at later maturation stages. We have now compared the ability of proanthocyanidin‐rich extracts from Carménère grape seeds collected at two stages of berry development (veraison vs. harvest) both to interact with salivary proteins and to produce astringency. Interaction of proanthocyanidins with the salivary protein was assessed by analysing the concentration‐dependent effect of seed extracts both on inducing salivary protein precipitation and on restricting diffusion of the salivary protein on cellulose membranes. Seed extracts from grapes collected at veraison compared with those of grapes collected at harvest displayed a higher ability both to interact with the salivary protein fraction and to produce astringency. As a whole, our observations show that astringency is closely dependent on the magnitude of the interactions between proanthocyanidins and the salivary protein fraction.     

“秒持值衡定评酒法”的研究与开发应用

秒持值衡定评酒法突破了传统评酒方式的局限性,使白酒的感观评定走上了数据化、标准化的科学轨道,提高了酿酒行业感观尝评技术的整体水平,使白酒感观评价具有更高的准确性,同时为感官尝评人员和酒体设计人员进行新产品的开发,工艺的改进,成本的降低,品质的保证与风味特征的优化等工作提供了最有效的工具。     

Control of sonoluminescence signal in deionized water using carbon dioxide

Megasonic cleaning is routinely employed in semiconductor industry for cleaning of wafers. However, the method also results in damage to wafer features and such damage has been proposed to arise from transient, imploding cavities formed during megasonic processing. Transient cavitation is associated with the release of light, a phenomenon called sonoluminescence (SL) and the extent of damage has been shown to correlate with the intensity of SL. Control of sonoluminescence may therefore allow control of damage during megasonic processing of wafers. In this study, the ability of carbon dioxide to quench sonoluminescence generation in deionized water exposed to megasonic field of varying power density and duty cycle has been systematically investigated. It has been found that CO₂ is not only incapable but also a potent inhibitor of sonoluminescence, providing a potential means for selective alleviation of the violent effects of transient cavitation in process fluids. A novel chemical method has been established for in situ release of CO₂ from NH₄HCO₃ through a pH induced shift in the carbonic acid equilibria in deionized water. Using this method, a precisely controlled, progressive decrease in SL of air saturated deionized water through addition of NH₄HCO₃ has been demonstrated. It has been determined that 130 ppm of released CO₂ is sufficient for complete inhibition of sonoluminescence generated in air saturated deionized water.     

Survival Analysis Applied to the Sensory Shelf-Life Dating of High Hydrostatic Pressure Processed Avocado and Mango Pulps

Abstract: High hydrostatic pressure (HHP) pasteurized and refrigerated avocado and mango pulps contain lower microbial counts and thus are safer and acceptable for human consumption for a longer period of time, when compared to fresh unprocessed pulps. However, during their commercial shelf life, changes in their sensory characteristics take place and eventually produce the rejection of these products by consumers. Therefore, in the present study, the use of sensory evaluation was proposed for the shelf-life determinations of HHP-processed avocado and mango pulps. The study focused on evaluating the feasibility of applying survival analysis methodology to the data generated by consumers in order to determine the sensory shelf lives of both HHP-treated pulps of avocado and mango. Survival analysis proved to be an effective methodology for the estimation of the sensory shelf life of avocado and mango pulps processed with HHP, with potential application for other pressurized products. Practical Application: At present, HHP processing is one of the most effective alternatives for the commercial nonthermal pasteurization of fresh tropical fruits. HHP processing improves the microbial stability of the fruit pulps significantly; however, the products continue to deteriorate during their refrigerated storage mainly due to the action of residual detrimental enzymes. This article proposes the application of survival analysis methodology for the determination of the sensory shelf life of HHP-treated avocado and mango pulps. Results demonstrated that the procedure appears to be simple and practical for the sensory shelf-life determination of HHP-treated foods when their main mode of failure is not caused by increases in microbiological counts that can affect human health.     

圆偏振光场中电离速率的研究

以Keldysh -Faisal-Reiss(KFR)的电离速率理论为基础 ,采用Yukawa函数 ,对氦原子和氙原子的电子能谱进行了计算 ,并将理论计算结果与实验结果进行了比较和分析 .结果表明 ,对于强场中稀有气体电离的电子能谱 ,此理论能够给出很好的解释和估计 ;同时对 10Hz、140fs、5 0mJ、795nm的掺钛蓝宝石激光系统驱动的圆偏振场电离 I0 =3× 10 16W /cm2 时的氪的电子能谱进行了理论计算 ,为研究基于光场感生电离的电子碰撞机制的类镍氪系统的实验奠定理论基础 .     

Onset of electrical conduction in isotropic conductive adhesives: a general theory

A new theory is introduced for the onset of electrical conduction in isotropic conductive adhesives, based on the observation that conduction is a result of the creation of conducting contacts in metal–insulator composite adhesives. The present theory resolves several prevalently contradicting issues including the onset dependency of electrical conduction on the volume fraction of filler particles, the particle size, the pressure effect, and the type of insulator matrix of an adhesive. The theory also predicts the condition for the occurrence of two percolation thresholds.